Investigation of an extract of the Australian marine sponge Psammoclema sp. for dynamin I inhibitory activity led to the isolation of four new trihydroxysterols (1−4) related to aragusterol G. These compounds were largely identified by 1D and 2D NMR spectroscopic methods. While 1 was found to be inactive in the dynamin bioassay, bioassays did reveal that compounds 1−4 inhibited the growth of colorectal, breast, ovarian, and prostate cancer cell lines (GI₅₀ 5−27 μM). The additional insight that these new compounds give to previous SAR studies is discussed briefly.